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Hydrostatic pressure-induced reversible phase transformation in iron oxide nanoparticles
Arkaprava Das1, Anumeet Kaur2, Parwinder Kaur3
1Chimie des Interaction Plasma surface, Université of Mons, Mons, Belgium. arkapravadas222@gmail.com.
Nanoscale
|June 18, 2024
Summary
Hydrostatic pressure reversibly transforms maghemite iron oxide nanoparticles (γ-Fe₂O₃) between cubic and tetragonal phases. This behavior, observed using a diamond anvil cell, is linked to the nanoparticles' core-shell structure and spin glass properties.
Area of Science:
- Materials Science
- Nanotechnology
- Solid State Physics
Background:
- Maghemite (γ-Fe₂O₃) nanoparticles exhibit unique magnetic and structural properties.
- Understanding pressure-induced phase transformations is crucial for advanced material applications.
Purpose of the Study:
- To investigate the hydrostatic pressure-induced reversible phase transformation in maghemite nanoparticles.
- To elucidate the relationship between structural changes, core-shell nanostructure, and spin glass behavior.
Main Methods:
- Synthesis of maghemite nanoparticles using thermal arc plasma.
- In situ high-pressure studies utilizing a diamond anvil cell (DAC).
- Analysis of structural and phase changes via Rietveld refinement and transmission electron microscopy (TEM).
Main Results:
- Reversible cubic ↔ tetragonal phase transformation observed in γ-Fe₂O₃ nanoparticles under pressures up to 2.58 GPa.
- Coexistence of cubic maghemite and metallic iron phases at 0.55 GPa.
- Core-shell nanostructure exhibits spin glass behavior, influencing magnetization and anisotropy.
Conclusions:
- The reversible phase transformation is driven by pressure-induced changes in spin glass shell behavior and internal stress.
- Atomic rearrangement and tetragonality arise from surface nucleation barriers and spin disorder.
- The "internal stress model" effectively explains the transition back to the cubic phase.
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